In a mobile communication system, if a building is built in the vicinity of a base station, or if an installation status of another base station in the vicinity of the base station changes, the radio environment related to the base station changes. Therefore, conventionally, an operator performs a drive test of measuring a radio environment by using a measurement vehicle mounted thereon with a measurement equipment, and collecting a measurement result and location information.
Such a measurement and collection can, for example, contribute to the optimization of a setting at the base station; however, there is a problem of too many man-hours and high cost.
In this regard, according to 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a mobile communication system, a specification design of MDT (Minimization of Drive Test) is under way which is a technology for automation of the measurement and collection by using a radio terminal owned by a user (see Non Patent Literature 1).
As a type of the MDT, there is a memory-type MDT (hereinafter, appropriately referred to as “Logged MDT”). In the Logged MDT, a radio terminal in an idle state measures a radio environment according to a measurement parameter set from a network, and stores a result of the measurement, together with location information and time information, as measurement data. Then, the radio terminal transitions to a connected state (on-communication state), and thereafter, reports the measurement data to the network later.